The present invention relates to the field of electrophoretic devices and, more particularly, to e-ink displays with an illuminating substance between surfaces of the display screen.
Due to the low power consumption and lightweight form factor, electrophoretic displays (EPDs) are becoming increasingly adopted to replace traditional displays such as liquid crystal displays (LCDs). Further, EPDs are being applied to address new solutions where previous technologies have been impractical. Electrophoretic display devices utilize an electronic field to rearrange charged pigment particles within a microcapsule, where the microcapsule is typically suspended in a transparent insulating material. The rearranging of the particles can cause light to be reflected off the particles which can be used to produce visible content on a display such as text and/or images.
One arena in which EPDs are gaining popularity is the electronic paper format category. Electronic paper format can be integrated into areas such as electronic book (e-book) readers, electronic newspapers, wearable displays, and the like. A common drawback of EPDs are their inability to function effectively in certain situations. Since EPDs are a reflective technology which relies on available (e.g. ambient) light, they can often perform poorly in low light situations. For instance, an e-book reader can become difficult to read at night due to insufficient incident light striking the surface of the device.
One solution for low light conditions that have been devised is the inclusion of an external book light attached to EPD devices such as e-book readers. Several problems with this solution exist which make it a less than ideal for many devices and scenarios. The external book light can be cumbersome to attach and position due to not being permanently fixed to the device. Additionally, the book light can provide uneven illumination of the viewing area resulting in a user having to constantly reposition the light to compensate. Further, external book lights can detract from the aesthetic appeal of the EPD which can be a major drawback for device manufacturers and consumers.
In many instances, an external light cannot be used to improve low light usability, rendering this option impractical. For instance, an external light would not be suitable for use with a electrophoretic display deployed at a night club venue. Other scenarios such as extremely low light and no-light environments can be problematic for EPD users.